The present invention generally relates to messaging systems, and, more particularly, to messaging systems within telecommunications systems.
In general, a messaging system enables the storage and supply of information to users in deferred mode and/or in immediate mode. Typically, a messaging system interconnected with an automatic branch exchange by at least one voice channel, so as to provide at least a voice service to user terminals connected to the automatic branch exchange. The term  less than  less than voice services greater than  greater than  is understood to mean any type of service based on the exchange of voice messages (also called audio messages) such as, for example, but not exclusively, mailboxes, announcements and automatic switchboard services.
A messaging system can also provide non-voice services based for example on the exchange of textual messages and/or image messages, or it can provide multimedia type services combining several types of messages.
An automatic branch exchange enables communications to be set up between two items of equipment located at distinct points in a network. The installations that are linked up are, for example, two user terminals or else one user terminal and one messaging system. The term  less than  less than user terminal greater than  greater than  refers especially but not exclusively to simple telephone sets and telephone sets providing enhanced functions (with screens).
A distinction is generally made between public automatic branch exchanges, which form part of the general telecommunications network, and private automatic branch exchanges or PABXs which do not form part of the network but fulfil the same functions (namely that of setting up communication between users of the network or networks).
Exchanges of service information required for inter-operation (or inter-operability) between the automatic branch exchange and the messaging system are referred to as signaling exchanges. Conventionally, these signaling exchanges are carried out on the voice channel (or one of the voice channels) interconnecting the automatic branch exchange and the messaging system. Indeed, the signaling messages are sent and received in the form of DTMF (dual tone multifrequency). Each signaling message consists of one or more DTMF codes assembled in a predetermined combination, generally proper to each messaging system provider. Each DTMF is itself defined by a pre-determined association of two voice frequencies (a high frequency and a low frequency). These values of frequencies are chosen so as to minimize the risk that each association resembles the breakdown of the voice.
This current approach, based on the transmission of DTMF codes in a voice channel, has many drawbacks.
First of all, the transmission of DTMF codes xe2x80x9cpollutesxe2x80x9d the voice channel whose primary function is the transmission of the voice.
Furthermore, the signaling transmission bit rate is limited to the bit rate of the voice channel used (which is generally 64 bits/second). In other words, the signaling exchanges between the automatic branch exchange and the messaging system, which are obligatorily designed as a function of the available bit rate, are restricted. This results especially in poor quality dialog (voice menus) and low-level information exchanges between the automatic branch exchange and the messaging system. This observation (poor quality dialog and low-level information exchange) can also be applied to a call, through the automatic branch exchange, between the messaging system and a subscriber terminal after a service of the messaging system has been started.
Additionally, security is reduced owing to the fact that signaling takes the same channel (and hence the same routing path) as the voice and that it is therefore impossible to transmit error or alarm messages once the voice channel is out of service.
Moreover, the coexistence of two types of information (namely voice information and signaling information) within one and the same voice channel is difficult to manage and can even prevent certain types of actions. Indeed, it is impossible to make only voice information undergo compression or again to make the signaling information undergo a different compression. Similarly, it is impossible to make only the voice information undergo encryption. Furthermore, the signaling information should be capable of being transmitted at any time.
Finally, in certain countries, especially Eastern Europe, the voice is sometimes identified with certain DTMF codes and generates false DTMF codes. These false DTMF codes then prompt errors in the signaling exchanges between the automatic branch exchange and the messaging system.
The invention is designed to overcome these different drawbacks of the prior art.
More specifically, one of the aims of the present invention is to provide a method of communication between an automatic branch exchange and a messaging system enabling an improvement in communication between these two elements and therefore an increase in the synergy between their functions.
It is also an aim of the invention to provide a method of this kind that enables an improvement in communication, through the automatic branch exchange, between the messaging system and a subscriber terminal after a service has been started by the messaging system.
Another goal of the invention is to provide a method of this kind enabling a dynamic allocation of resources of the messaging system.
An additional goal of the invention is to provide a method of this kind enabling the creation and implementation of a generic signaling protocol between the automatic branch exchange and the messaging system.
Yet another goal of the invention is to provide an automatic branch exchange and a messaging system enabling the implementation of a method of communication of this kind.
The above goals, as well as others goals, are achieved according to the invention by using at least one signaling channel to interconnect an automatic branch exchange and a messaging system. The automatic branch exchange and the messaging system being also interconnected by at least one voice channel so as to implement the at least one voice service on the messaging system. The signaling channel is distinct from the at least one voice channel. The signaling channel at least partially bearing signaling exchanges between the automatic branch exchange and the messaging system.
The invention modifies the communication interface between the automatic branch exchange and the messaging system by adding at least one signaling channel in parallel with the commonly used voice channels. In this way, the automatic branch-exchange and the messaging system can exchange signaling without any voice channel being  less than  less than polluted greater than  greater than  by DTMF codes. More generally, the present invention makes it possible to overcome all the above-mentioned drawbacks directly related to the use of the DTMF codes. In particular, since the signaling transmission bit rate is independent of the voice transmission bit rate, the signaling transmission bit rate may be as high as desired. An increase of this kind in the quantity of signaling exchanged makes it possible to increase the synergy between the automatic branch exchange and the messaging system. It provides, for example, for a dynamic allocation of resources of the messaging system. It also enables the designing of extensive and highly developed forms of dialog as well as fuller exchanges of information between the automatic branch exchange and the messaging system. This extensive range of communication may also be of benefit to exchanges between the messaging system and the user terminal when these units communicate through the automatic branch exchange after a service of the messaging system has been started. These extensive and highly developed forms of dialog are obtained, for example, if the user terminal has a screen and a keyboard, in the form of visual scrolling menus. Indeed, these menus are far more user-friendly and much faster to use than the currently proposed voice menus.
Furthermore, the same automatic branch exchange can be interconnected to several messaging systems. In this case, it is enough to apply the method according to the present invention for each of the distinct messaging systems interconnected with the automatic branch exchange.
Preferably, the signaling channel is a digital type channel.
Also preferably, a generic signaling protocol is implemented in the at least one signaling channel. The generic character of this signaling protocol makes it usable with all types of automatic branch exchanges and messaging systems. It is therefore not a xe2x80x9cmanufacturer protocolxe2x80x9d related to a particular type of system.
The generic signaling protocol may include a normal phase of operation during which the automatic branch exchange and the messaging system implement at least one predetermined signaling exchange. The generic signaling protocol may further include an initializing phase during which the messaging system transfers an image of its current configuration to the automatic branch exchange so that the automatic branch exchange adapts its operation to that of the messaging system. The knowledge by the automatic branch exchange of the current configuration of the messaging system enables the automatic branch exchange to optimize its inter-functioning with the messaging system, especially when a user terminal asks for access to one of the services of the messaging system.
Advantageously, during the initializing phase, the automatic branch exchange transfers an image of its current configuration to the messaging system so that the messaging system adapts its operation to that of the automatic branch exchange. The knowledge, on the part of the messaging system, of the current configuration of the automatic branch exchange enables the messaging system to optimize its inter-functioning with the automatic branch exchange.
Preferably, the image of the current configuration of the messaging system and/or the image of the current configuration of the automatic branch exchange are images according to object-oriented models.
According to an embodiment of the invention, the at least one voice channel also bears a part of the signaling exchanges.
In a preferred embodiment of the invention, the automatic branch exchange and the messaging system exchange signaling messages on at least one signaling channel within the framework of the generic signaling protocol. The signaling messages include:
a xe2x80x9cclassxe2x80x9d field enabling the identification of one class in a group of at least one possible class;
an xe2x80x9cinstancexe2x80x9d field that is either not defined or enables the identification of a particular instance in a group of at least one possible instance for the identified class in the xe2x80x9cclassxe2x80x9d field;
a xe2x80x9cnature of messagexe2x80x9d field enabling the identification of a nature of the message from a group of least one nature of message possible for the identified class in the xe2x80x9cclassxe2x80x9d field;
possibly a xe2x80x9cparameter(s)xe2x80x9d field that is either not defined or enables the identification of at least one parameter associated with the nature of message identified in the xe2x80x9cnature of messagexe2x80x9d field.
This message structure makes it possible to create a very large number of distinct signaling messages and facilitate their processing.